Within the context of this disclosure, the expression “engine” encompasses internal combustion engines and, in particular, applied-ignition Otto-cycle engines but also hybrid engines, that is to say engines which are operated using a hybrid combustion process, and diesel engines.
In the development of engines, it is generally sought to minimize fuel consumption and reduce exhaust emissions.
The traditional Otto-cycle engine operates with a homogeneous air-fuel mixture, wherein setting the desired power is achieved by quantity regulation and varying the charge of the combustion chamber. By adjusting a throttle flap which is provided in the intake tract, the pressure of the inducted air downstream of the throttle flap can be reduced to a greater or lesser extent. For a constant combustion chamber volume, it is possible in this way for the air mass to be set by means of the pressure of the inducted air. However, quantity regulation via a throttle flap has thermodynamic disadvantages in the part-load range due to throttling losses. Thus, in Otto-cycle engines particularly, minimizing fuel consumption can be challenging.
One approach for dethrottling the Otto-cycle engine working process that has been implemented in the development of hybrid combustion processes is based on the transfer of technical features of the traditional diesel engine process. These features may include air compression, inhomogeneous charge mixtures, auto-ignition, and quality regulation. The low fuel consumption of the diesel engine may result largely from quality regulation, in which the load is controlled by means of the injected fuel quantity.
The injection of fuel directly into the combustion chamber of a cylinder is therefore considered to be a suitable method for noticeably reducing fuel consumption, even in Otto-cycle engines. The dethrottling of the engine may be achieved by quality regulation being used within certain limits.
To initiate the applied ignition in a direct-injection Otto-cycle engine, the engine may be equipped with an ignition device, such as an ignition plug. Thus, one task during the structural design of the combustion chamber is providing a coordinated arrangement of the injection nozzle and ignition device in the combustion chamber, which is often difficult due to the very limited space availability in the cylinder head of the engine.
For these reasons, the injection nozzle is often arranged in the cylinder head eccentrically and spaced apart from the longitudinal axis of the cylinder, as described in the present disclosure. According to an embodiment, an injection nozzle which opens outwardly may be used for the injection of the fuel and is opened by virtue of the nozzle needle being moved into the combustion chamber. The open nozzle has an annular gap between the nozzle body and needle, through which fuel is introduced into the combustion chamber.
Such an arrangement of the injection nozzle has a disadvantageous effect on the mixture formation in the combustion chamber. In particular, there may be a conflict between the eccentric arrangement of the nozzle and the introduction of a fuel cloud with uniform mass distribution into the combustion chamber via the annular gap. That is to say, the asymmetrical arrangement of the nozzle in the combustion chamber may conflict with the formation of a uniform and symmetrical fuel cloud for efficient combustion and decreased emissions. Furthermore, the injection nozzle is often also inclined with respect to the longitudinal axis of the cylinder, which may further intensify the described disadvantages.
The fuel cloud of homogeneous form and uniform mass distribution in interaction with the eccentric, possibly inclined installation position of the nozzle, contributes to a fuel distribution in the combustion chamber that has an adverse effect on the combustion and the formation of pollutants, in particular the emissions of unburned hydrocarbons and soot.
Thus the inventors sought to provide a direct-injection engine wherein the above disadvantages resulting from the eccentric installation position of the nozzle art are reduced or eliminated. They found that this could be achieved in part in an embodiment wherein a direct-injection engine has at least one cylinder in which a combustion chamber is jointly formed by a piston crown of a piston, which is movable along the longitudinal axis of the cylinder, a cylinder head, and an injection nozzle, which is arranged in the cylinder head on the opposite side of the piston crown eccentrically and spaced apart from the longitudinal axis of the cylinder. For the direct injection of fuel, the injection nozzle may have a nozzle needle which is movable in a nozzle body which serves as a nozzle housing, wherein the needle, when transferred into the open position of the nozzle by being moved into the combustion chamber, opens up an annular gap arranged between the nozzle body and needle. One or more guide elements that influence the fuel flow are provided on a surface of the nozzle.
Therefore, by redirecting some of the fuel flow inside the injector via the guide elements, a non-uniform inflow condition may result and thus cause uneven flow distribution at the nozzle exit. The injector may therefore be tuned for off-center injection placement and aligned for deflection of air movements.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.